This invention relates to semiconductor devices having more than one electrical circuit component formed in a semiconductor device body. Such a semiconductor device may be, for example, an integrated circuit, having analogue and/or digital circuits. Otherwise such a semiconductor device may be, for example, a semiconductor power device with one or more protection devices.
Semiconductor devices as just described usually have more than one circuit component in the device body connected to a same electrical terminal, and it may be desired to provide for independent testing of these components before connecting them to this terminal. It is also desirable to minimise the number of terminal connections, for example bonded wires or straps, from the semiconductor device body.
It is known to achieve both of the two just described objectives by providing a semiconductor device as disclosed in U.S. Pat. No. 4,223,337, WO-A-98/08250, U.S. Pat. No. 5,900,643 and U.S. Pat. No. 5,892,283, the whole contents of which are hereby incorporated herein as reference material. These known prior art arrangements include:
a semiconductor device body having first and second electrical circuit components formed therein;
an electrical conductor layer formed on said semiconductor device body, said conductor layer including a first bond pad portion electrically connected by said layer to said first circuit component and said conductor layer including a second bond pad portion electrically connected by said layer to said second circuit component, said first and second bond pad portions being formed separated and electrically isolated from each other, thereby permitting independent electrical testing of said first and second circuit components prior to electrical connection of the first and second bond pad portions to a same electrical terminal; and
terminal connection means bonded at one end thereof to the said first and second bond pad portions to electrically connect those portions on said device body, said terminal connection means being connected at another end thereof to said electrical terminal.
An aim of the present invention is to provide a semiconductor device in which, inter alia, disadvantages of these prior art arrangements are overcome or reduced.
According to the present invention there is provided a semiconductor device including first and second bond pad portions electrically connected to respective first and second circuit components by a conductor layer, wherein the first and second bond pad portions are separate from each other, thereby permitting independent electrical testing of the first and second circuit components prior to electrical connection of the first and second bond pad portions to a same electrical terminal; and wherein the device is characterised in that the first and second bond pad portions each has a respective set of parallel fingers disposed in an interdigitated pattern, which defines a bond pad area; and in that the terminal connection means comprises an elongate portion bonded to said device body over a substantially rectangular bonded region with the length of said bonded region extending in a direction across the fingers of said interdigitated bond pad area.
The combination of these characterising features of the present invention, allows for a large misalignment in the bonding process, as performed by auto-bonding machines, while nevertheless achieving connection of the first and second bond pad portions and hence connection, after testing, of the first and second electrical components to the same electrical terminal. Thus, misalignment of the bonded region along nearly the whole length of the fingers of the two sets of parallel fingers, that is to say across the width of the bond pad area will still connect the two sets of fingers. Also, even if there are only two fingers in each set this will provide three gaps along the length of the bond pad area such that if any one of these gaps is bridged by the bonded region then the first and second bond pad portions will be connected. If the bonded region is misaligned in both directions towards a corner of the bond pad area, and possibly also skewed, there is still a high probability that at least one finger from each of the two sets will be covered and the first and second bond pad portions will be connected.
The first circuit component of the semiconductor device of the invention may be a semiconductor power device having first and second main electrodes and a control electrode, the first bond pad portion being connected by the conductor layer to one of these electrodes of the power device. This power device may be a power transistor device, the first electrode being a drain electrode, the second electrode being a source electrode, and the control electrode being a gate electrode. Suitably in this case the second circuit component is a protection device connected between the gate electrode and one of the drain and source electrodes for protecting the power transistor device. A preferred arrangement with a protection device connected in this way is where the first bond pad portion is connected by the conductor layer to the gate electrode of the power transistor. In this preferred arrangement the protection device may be an electrostatic discharge (ESD) diode protection device, or it may be a voltage clamping diode protection device.
Prior art document U.S. Pat. No. 4,223,337 mentions an electrode pad being divided into plural parts without being any more specific, and prior art document WO-A-98/08250 mentions that more than two bonding pads may be involved, for example in a radial orientation which would be problematic. By contrast, the combination of characterising features of the present invention as defined in the preceding main statement of the invention very readily lends itself to having more than two bond pad portions for independent testing of corresponding more than two electrical components which are then connected to a same terminal.
Thus in a semiconductor device in accordance with the invention, the semiconductor device body may have a third electrical circuit component formed therein, and a respective third bond pad portion may be electrically connected by the conductor layer to the third circuit component, the third bond pad portion being separate from the first and second bond pad portions, thereby permitting independent electrical testing of the third circuit component prior to electrical connection of the first, second and third bond pad portions to said electrical terminal. The terminal connection means may be bonded at the one end thereof to the first, second and third bond pad portions to electrically connect those three portions on the said device body. Thus, the third bond pad portion may have a respective third set of parallel fingers disposed to overlap at least one the first and second sets of fingers such that the bond pad area is defined by the interdigitated pattern formed by the first, second and third sets of fingers; and with the length of the substantially rectangular bonded region extending in a direction across the first, second and third sets of fingers of the interdigitated bond pad area.
A suitable implementation for the arrangement just defined is where the first circuit component is a power transistor device having a drain electrode, a source electrode and a gate electrode, where the first bond pad portion is connected by the conductor layer to the gate electrode, where the second circuit component is an electrostatic discharge (ESD) diode protection device connected by the conductor layer between the second bond pad portion and one of the drain and source electrodes, and where the third circuit component is a voltage clamping diode protection device connected by the conductor layer between the third bond pad portion and the other of the drain and source electrodes.
In a semiconductor device according to the present invention, at least one set of parallel fingers preferably has at least three parallel fingers in that set. In this case, at least one set of parallel fingers may have all the fingers of the set connected by the conductor layer outside the bond pad area at one end of the fingers of that set. Alternatively, or in addition, at least one set of parallel fingers may have successive pairs of the fingers of that set connected by the conductor layer outside the bond pad area at opposite ends of the fingers of that set to form a serpentine conductor layer path with the fingers of that set. For example, in the case of three bond pad portions connected respectively to the gate electrode of a power transistor, an ESD protection device and a voltage clamping device the arrangement may have the fingers for the ESD protection device connected at their one end, the fingers for the voltage clamping device connected at their other end, and the fingers for the gate electrode connected in a serpentine path and interdigitated with both the other two sets of fingers.
In a semiconductor device according to the present invention, the terminal connection means may be a metal wire which is wedge-bonded at the one end thereof to the bond pad portions. The length of the bonded region may be at least three times the diameter of the metal wire. This facilitates connection of more than two bond pad portions, and also helps to ensure connection of the bond pad portions taking into account misaligned placement of the bonded region. Alternatively the terminal connection means may be a metal strap which is bonded at the one end thereof to the bond pad portions.
In a semiconductor device according to the present invention, the conductor layer may provide a test pad for each circuit component outside the bond pad area for the independent electrical testing of that circuit component.